Foot operated parking brake controls for motor vehicles are well known. Conventionally, these devices provide a brake pedal that is secured to the end of a brake cable. The pedal is arranged to tension the cable by pivotal movement. A holding device, such as a pawl and ratchet, holds the pedal and cable in a brake applied position. The holding device may be released so that the cable and brakes will be displaced at an at-rest position.
The present invention provides an improvement in parking brake controls for motor vehicle brake systems. In order to improve the tensioning capability of the parking brake control while maintaining a desired level of operator effort, a parking brake control having a pedal that may be stroked a plurality of times is provided. The control of this disclosure permits a desirable high mechanical advantage ratio so that the parking brake cable may be properly tensioned while permitting operator effort at the brake pedal to be within acceptable limits.
In its presently preferred embodiment, this invention provides a parking brake control that includes a rotatably supported pulley which is connected to a brake cable. A large gear is affixed to the pulley. A pivotally supported brake pedal carries a rotatably mounted driving pinion in mesh with the large gear of the pulley. A one-way helical spring clutch interconnects the pedal and the driving pinion. The spring clutch is constructed (1) to hold the pinion fast with the pedal when the pedal is moving in a direction that tensions the brake cable and (2) to permit rotation of the pinion when the pedal is moving toward its retracted position.
A holding pinion is rotatably supported on the housing and is in mesh with the large gear. A one-way helical spring clutch interconnects the holding pinion and the housing. The spring clutch is constructed (1) to permit unrestricted rotation of the holding pinion with respect to the housing when the large gear and pedal are moving in a direction to apply the brakes and (2) to hold the holding pinion and large gear in a brake applied position when the vehicle operator releases the pedal.
A release mechanism is provided in association with the second spring clutch to permit the large gear, brake cable and pulley to return to the released position under the force of a return spring when the release mechanism disengages the second clutch from the holding pinion.
The preferred construction provides a parking brake control in which the pedal may be stroked a plurality of times by a vehicle operator until the parking brake cable is tensioned to a desired level.